Manufacture of motor fuel



Aug. 21, 1945. A. R. GoLDsBY MANUFACTURE OF' MOTOR FUEL 2 Sheets-Sheet 1 F'iled Jan. 25, 1941 ARTHUR EGOLDsY d /N VENTO/e All A T ORNE V5 Aug, 21, 1945. A. R. GoLDsBY 2,383,056

MANUFACTURE OF MOTOR FUEL V Filed Jan. 25, 1941 2 Sheets-Sheet 2 Patented Aug. 21, 1945 MANUFACTURE OF MOTOR FUEL Arthur R. Goldsby. Beacon, N. Y., assignor, by mesne assignments, to The Texas Company, New York, N. Y., a corporation of Delaware Application January 25. 1941, Serial No; 375,918

1s claims. (ci. 26o-esas) This invention relates to the manufacture of motor fuel and particularly to a process of treating naphtha involving alkylation of certain hydrocarbon constituents of naphtha.

The invention broadly contemplates treatingnaphtha to remove sulfur bodies, gum-forming constituents and other impurities. In addition it contemplates separating from th'e naphtha. an oleflnic fraction which is substantially free from 'aromatic and other constituents ,and therefore in a condition which is particularly suitable for` alkylating isoparamn hydrocarbons to produce additional gasoline hydrocarbons of high antiknock value.

More particularly, the invention contemplates treating naphtha with sulfuric acid or other renning agent so as to effect removal of unsaturated and ol'enic constituents and produce a color and gum stable naphtha retaining aromatics and other constituents suitable for motor fuel. Oleflnic constituents so removed from the naphtha are utilized, all or in part, for the alkylation of low boiling isoparaflin hydrocarbons and thereby produce an additional yield of high antiknock motor fuel.

An important object of the invention involves segregating the normally liquid olefinic constitemperature, that is in the range about l0 to 60 F. and preferably at a temperature of about l0 t0 30 F. Under these conditions the concentrated acid dissolves olefinic hydrocarbons without appreciably affecting other desirable constituents of the naphtha. After removal of the acid and dissolved hydrocarbons the remaining acid treated naphtha is neutralized with caustic soda solution or other alkaline neutralizing agent to produce a treated gasoline having an antiknock value usually not substantially lower than that of the raw naphtha.

tuents of naphtha or gasoline and then using them to alkylate isoparaflin hydrocarbons in the substantial absence of non-oleflnic constituents of the naphtha or gasoline which interfere with the alkylation reaction and whose presence in the final product may be undesired. As a consequence an improved yield of alkylate of improved octane number is obtained as well as a decrease in catalyst deterioration.

A further object is to remove from the hydrocarbon feed to an alkylation reaction those constitutents such as diolens, sulfur compounds, etc., which if present in the alkylation reaction result in decreased catalyst life. g

- The invention is illustrated in the attached drawings which show preferred embodiments thereof, and wherein:

Fig. 1 is a diagrammatic illustration of apparatus for carrying out the method of the present The acid and dissolved hydrocarbon constituents are conducted to an alkylation process wherein the dissolved hydrocarbons are reacted with isobutane in the presence of concentrated sulfuric acid under alkylation conditions where.- by the isobutane is converted to branched chain gasoline hydrocarbons having a high antiknock value. The gasoline produced in the alkylation operation may be blended all or in part with the acid-treated gasoline or separately disposed'of in whatever manner desired.

According to another modeof operation also illustrated in Fig. 1, cracked naphtha is preliminarily treated in conventional manner toremove gum-forming and color-forming bodies, presumably consisting mainly of diolens, which cause an increase in the catalyst consumption during alkylation. Subsequently it is treated with acid under suitable conditions to remove .at least a substantial proportion of the remaining olefins namely, mono-olefins, While leaving 4 valuable aromatic constituents in the treated naphtha.

The olefins removed in the second acid treatl ing operation will comprise mono-oleiins substantially free from diolens and therefore will provide a purified olefinic charge for the alkylation f fins is already highly concentrated it can be used to advantage to form at least a, part of the catalyst employed in a sulfuric acid alkylation operation.

According to another modification illustrated in Fig. 2 the naphtha, either with or without the preliminary treatment to remove gum-forming constituents, may be treated with liquid sulfur dioxide or other selective solvent to extract from the naphtha. a fraction consisting essentially of normally liquid olens and aromatics. The fraction so extracted from the naphtha, after removal of the solvent, is then treated with sulfuric acid to segregate thereform a fraction consisting essentially of oleilns substantially free from aromatic and other constituents including paraillnic constituents. The olens thus obtained are passed to the alkylation reaction with or without the acid in which they were absorbed.

The process may be modiiied to effect removal of the colorand gum-forming constituentsfrom the naphtha, or from the above-mentioned olen-aromatic fraction extracted from the naphtha, by treatment with.- cuprous chloride, by solvent extraction, by treatment with acid, by contact with an adsorptive contact material such as acid treated clay, fullers earth or other similar type material. Following this preliminary treatment the naphtha is treated with concentrated acid under non-alkylating conditions to extract the oleilns.

Advantageously, the cracked naphtha, after removal of the gum-forming and color-forming constituents either by acid treatment r by contact with an adsorptive agent, is neutralized and subjected to steam distillation so as to separate undesired high boiling material, as shown in Fig. 1. Thereafter, olefin constituents are extracted from the naphtha to produce a treated naphtha retaining aromatic constituents and having a high antiknock value.

The conditions under which the acid treatment or treatments is effected will depend upon the nature or source of the cracked naphtha and also upon the nature of the particular products desired. For example, the nature of the acid treatment may depend upon whether the motor fuel product is for use in an aviation motor or in an automobile motor. Thus, in the case of an aviation motor fuel it is desirable that the product have a low unsaturated content as indicated by a low acid heat, and a low gum content. The extent to which it is desired to reduce the unsaturated content of the product governs the extent of the acid' treatment or extraction. On the other hand, it will depend on the nature of the olefinic fraction which it is desired to segregate from the naphtha as a charge to the alkylation reaction.

It has been found that by subjecting cracked naphtha to treatment with concentrated sulfuric acid at relatively low temperature oleiinic constituents can be extracted from the naphtha without removing substantial amounts of the aromatic, naphthenic and paraftinic constituents. Thus, the treated gasoline may have an octane number not substantially lower than that of the raw naphtha.

As indicating the nature of the acid treating step a cracked naphtha of about 284 F. end boiling point and having a CFRM octane number of 78.5v was treated with 98% sulfuric acid at a temperature of 20 F. in the proportion of 18 lbs. of acid per barrel' of naphtha. The treated naphtha was neutralized and steam distilled to produce a treated product having a CFRM octane number of 77.1. The treated product amounted to about 90% by volume of the raw naphtha charged to the acid treating step, and had an acid heat value (determined by method D481-39 ASTM) of 10 F. as compared with an acid heat of about 100 F. for the raw naphtha. 'Ihe treated product was further characterized by having a gum content of not in excess of 'I mg. per 100 cc. gasoline (copper dish test).

Consequently, the constituents dissolved and removed in the acid consist mainly ot oleiins and are, therefore, suitable for alkylating isobutane to produce gasoline hydrocarbons. The absence of aromatic constituents from the hydrocarbon charge to such an alkylation operation is desirable because such aromatics, if present in the sulfuric acid alkylation reaction, cause an increase in the catalyst consumption. In addition they result, for the most part, in the formation of alkylated hydrocarbons boiling outside the range for gasoline.

The invention illustrated in Fig. 3 also provides a method for processing cracked hydrocarbon fractions containing aromatic constituents whereby aromatic constituents such as toluene can be segregated for other purposes in more concentrated form. For example, a low boiling cracked hydrocarbon fraction, containing C5, Cs and C7 hydrocarbons including toluene, can be treated with concentrated' acid at low temperature so as to absorb the oleiinic constituents while leaving the aromatic and parafnic constituents undissolved. The olefinic hydrocarbons can be reacted with isobutane in the presence of concentrated sulfuric acid under alkylating conditions to produ-ce valuable gasoline hydrocarbons. 'Ihe undissolved aromatic and other constituents can be extracted with a suitable solvent to separate the aromatics from the pararllns and naphthenes.

The process is applicable to the treatment of either low boiling or high boiling cracked naphtha containing oleflnic and aromatic constituents or to the treatment of various fractions of such naphtha. Thus, the invention is applicable to the treatment of gasoline or naphtha produced in the thermal conversion of hydrocarbons. with or without catalysts, and also to the treatment of naphtha reformed either with or without catalysts, or to hydroformed naphtha. It is also applicable to the treatment of naphthas which are composed mainly of olenic and parainic constituents.

In order to describe the invention in more detail reference will now be made to Fig. 1 of the accompanying drawings showing one method of ow suitable for carrying out the invention.

Referring to the drawing cracked naphtha such as produced in a conventional cracking operation is conducted from a source not shown through a pipe I to a stabilizer unit 2. The stabilizer is operated under conditions such as to remove from the naphtha normally gaseous hydrocarbons comprising C4 and lighter hydrocarbons. Gaseous constituents such as methane and ethane are removed through a pipe 3 while a side stream v comprising mainly C3 and C4 hydrocarbons is drawn oil through a pipe 4. This fraction will comprise -propy1ene, propane, butylenes, normal butane and isobutane. It is conducted all or in part to an alkylation unit 5.

In the alkylation unit the oleiln constituents are reacted with isobutane in the presence of concentrated sulfuric acid whereby branched chain hydrocarbons are formed. Concentrated acid, namely, acid containing about 96 to 100% H2804 is introduced through a pipe 6 while additional isobutane may be introduced to the alkylation unit through a pipe l.

The alkylation reaction may be effected under pressure and at a temperature of about 30 to 50 F. A substantial excess of isobutane over olens is maintained, for example, a ratio of isobutane to oleilns in the feed ranging about 5:1 to 15:1 or

aesaoso A v3 higher. The proportion of acid is ordinarily about l part by volume or more to 1 part of hydrocarbon in the reaction system. The time of reaction may vary from about 10 minutes to 1 hour.

Spent acid of about 85 to 90% concentration is discharged from the alkylation unit through a Pipe 8 while the hydrocarbons are conducted to a neutralization unit 9 wherein they are treated with caustic or other alkaline agent for the purpose of neutralizing and removing retained acid.

The used acid drawn oi! from pipe 8 may be conducted through a branch pipe 8a for use in the acid treatment of the stabilized naphtha and to which further reference will be made.

The alkaline sludge is drawn oil through a pipe I while the neutralized hydrocarbons are conducted through a pipe II to a fractionation unit I2.

In the operation of the fractionation unit light gaseous materials are discharged through a pipe- I3 while a side stream comprising isobutane is drawn oli through a pipe I4. All or a portion of the isobutane produced from the fractionation unit may be recycled through a pipe I5 to the al kylation unit 5 previously referred to.

Alkylated hydrocarbons boiling within the range suitable for motor fuel are drawn oil? through a pipe I6 and all or a part conducted through a branch pipe Il to a tank I8. i

Higher boiling constituents contained in the al. kylated hydrocarbons are withdrawn from the fractionation unit through a pipe 20 and i! desired a portion of these higher boiling constituents may be recycled to the alkylation unit. These higher boiling constituents can also be usedr as a source of safety fuel.

Referring again to the stabilizer unit 2 the stabilizer cracked naphtha is drawn oli through a pipe 25 and according to one Inode of operation, conducted to preliminary acid treating unit 26, the purpose of which is to remove colorand gum-forming constituents such as dioleflns.

In this preliminary acid treatment, for example, about 93% H2SO4 is. introduced to the treatlng unit through a, pipe 2l. This acid may be in- 45 troduced inthe proportion of about 2 to 3 lbs. of acid per barrel of stabilized naphtha. The acid and naphtha are subjected to intimate mixing at about 60 to 90 F. as, for example, by means of a turbo-mixer during which the acid is in con- 5o tact with the naphtha for a relatively short period of time, such as about 30 to 60 seconds. Separation of the acid and dissolved constituents from the treated naphtha may be effected by settling or by centrifugal means.

The acid treatment effected at this stage of the process is of relatively mild nature. Consequent- -ly, it may be desirable to employ even weaker acid, for example, acid of about 60 to 75% concentration, and effect the treatment at about room temperature or at higher temperatures up to about 150 F., for example.

The acid and dissolved hydrocarbon constituents are withdrawn and conducted through pipe 28 and discarded or disposed of in any desired 6 still 3i in order to remove undesired high boiling 7 constituents.

1o a pipe 35 from a source not shown. As in the case ci the acid treating unit the acid and naphtha are subjected to intimate contact as, for example, by passage through a turbo-mixer. l'Ihe proportion of acid used will depend upon the amount of oleilnic material it is desired toextract from the naphtha. Thus, the acid used may be in the` proportion ranging from about 10 to 50 lbs. o! acid per barrel of naphtha.

,The treatment may be carried out at a temo perature in the range of 10 to 60 F. but preferably at a temperature about 10 to 30 F., employing a time of contact between acid and naphtha of about 30 to 60 seconds. Y

'Ihe acid treated naphtha is conducted to a neutralizing unit 30 wherein it is subjected to contact with an alkaline material to produce a neutral product which is removed through a pipe 31. This product may be conducted allor in part by line 33 to the previously mentioned tank I8 wherein it may be blended with the gasoline hydrocarbons formed in the alkylation operation. Where the raw naphtha feed is of such nature that the acid treated naphtha from the treater 33 is of lower antiknock value than desired it 35 may be subjected to a thermal or catalytic reforming action, or may be supplied by line 40 to fractionating unit 4I. and tractionally distilled and the higher boiling -iraction or fractions thereof supplied by line 42 to reforming unit. 4o and subjected to reforming.

The reformed naphtha may then be conducted by line M to the fractionator 2 for treating as already de' scribed, and the light naphtha fraction passed by line 45 for blending in tank I8.

The acid mixed with the olens extracted from the naphtha in the acid treating unit 33 is withdrawn through a pipe 38 and conducted to the previously mentioned alkylation unit 5.

'I'he olens extracted from the naphtha in the acid treating unit 33 will comprise hydrocarbons having from 5 to 11 carbon atoms per molecule and preferably comprising olelns having from 5 to about 9 carbon atoms per molecule.

It is contemplated that the olens associated with the acid, probably in the form of esters, withdrawn through the pipe 38 may be extracted from the acidprior to introduction to the alkylation operation. By so doing a weak acid, for example, of about -90% H2804 may be employed to extract the olens from the naphtha, Such extraction may be eiected, for example, by treating the mixture of acid and absorbed oleflns with a substantial quantity oi isobutane under conditions such that the olelns are separated from the acid. The resulting mixture of isobutane and olenns is then passed to the alkylation reaction.

It is also contemplated that the mixture oi oleiins and acid drawn oil.' from the acid treatingvunit 33 may be used to alkylate isobutane or other low boiling isoparaflln hydrocarbons either in the presence or absence of olefin hydrocarbons obtained from extraneous sources.

The olens dissolved in acid and drawn Ii`through the pipe 33 may be polymerized and removed from the acid. 'I'he oleilns thus separated as polymers from the acid can be used to alkylate an isoparailln hydrocarbon.

Fig. 2 discloses the unstabilized cracked naphtha feed to a fractionator 50 from which C. and lighter is passed overhead as a charge stock for alkylation, and the stabilized cracked naphtha bottoms are removed to a gum removal unit 5| where the naphtha is treated with weak acid in the manner previously described. The treated naphtha is then passed to a solvent unit 52 where it is extracted with a selective solvent for oleilns and aromatics in the manner described above. The naphtha raffinate is separated by line 53 from the solvent extract, which latter is passed to the solvent separation unit 54 where the solvent is removed from the oleflnic and aromatic hydrocarbons. The latter are then treated in the acid treating unit 55 with strong sulfuric acid under the conditions previously described to effect selective olefin removal, from which an aromatic hydrocarbon layer is separated and recovered.

The acid-olen'extract may be passed directly by line 56 to the alkylation unit 51, or passed by line 5B to the ester ,extraction unit 59 where the absorbed olefin is extracted from the acid by means of an lsoparailin such as isobutane as previously described. The resulting isoparafllnolefin extract is then passed tothe alkylation unit 51. The resulting alkylate produced in the alkylation unit, or a selected fraction thereof, is passed to the blending tank 60.

'I'he naphtha rainate from line 53 may be passed directly by line 5I to the reforming unit 62, or may be passed by line 63 to the fractional distillation unit 64 where it is separated into a light fraction that is passed by line 55 to the blending tank 50, and a heavy fraction that is passed by line 66 to the reforming unit 52. Products of the reforming operation are returned by line 51to fractionator 50.

In accordance with the method of Fig. 3, the unstabilized cracked naphtha is stabilized in fractionator 10, the resulting stabilized cracked naphtha treated for gum removal inv treater 1|, and the treated naphtha then passed to acid treating unit 12. In the latter it is subjected to the action of strong sulfuric acid for selective olefin removal in the manner previously de scribed, and the resulting acid-olefin extract is supplied to alkylation. 'I'he hydrocarbon layer containing paraflins, naphthenes, and aromaticsI passes to the solvent extraction unit 13 where it is Ytreated with a selective solvent as previously described to recover an aromatic extract. The resulting naphtha railinate, from which olefins and aromatics have been removed, then passes to the fractional distillation unit 14 from which a light naphtha fraction is removed overhead for blending with the alkylate. The heavy naphtha fractionAremoved as bottoms 'from fractionator 14 is then reformed in reforming unit 15, and the reformed products returned by line 16 to fractionator 10.

The alkylation reaction may be effected by means furic acid. As examples of such catalysts mention may be made of BFmhO where n has a value ranging from 1 to 1.5. vStill other ex' amples are liquid'hydrogen fluoride; the metallic halides such as AlCls used in conjunction with a hydrogen halide such as HC1; chlorsulfonic acid,

etc. l As already indicated an important object i o'f catalysts other than concentrated sulassauts the alkylation step is to effect reaction of a normally gaseous isoparailln with an oleiin hydrocarbon in the presence of an alkylatlon catalyst maintained under alkylating conditions so as to 5 form Anormally liquid branched chain hydrocarbons of high antiknock value. The alkylation step is generally similar to and may be carried out in a manner substantially similar to that disclosed in the Goldsby-Watson U. S. Patent No.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereofl and therefore only such limita- -tions should be imposed as are indicated in the appended claims.

I claim:

l. In the manufacture of motor fuel of high antiknock value the method which comprises 2o treating naphtha containing oleilnic and aromatic constituents with concentrated sulfuric acid of 96-100% strength at a temperature of about 10-60 F. and with short contact time such that olefin constituents of the naphtha coextensive in Aboiling range with aromatic constituents thereof are preferentially absorbed by the acid without any substantial absorption of the aromatic constituents, separating the acid and absorbed oleilns from the naphtha, passing absorbed oleflns substantially free from aromatica to an alkylation zone and subjecting the mixture therein to contact with a substantial molar excess of low-boiling isoparafiin in the presence of an alkylation catalyst maintained under alkylating conditions whereby branched chain gasoline hydrocarbons of high antiknock value are obtained.

2. In the manufacture of motor fuel of high antilmock value the method which comprises treating naphtha containing parafllnic, aromatic trated sulfuric acid of sas-100% strength at a temperature of about lil-60 F. and with short contact time such that oleflnic constituents coextensive in boiling range with aromatic constituents thereof are preferentially absorbed in the acid without any substantial absorption of the aromatic constituents, removing the acid and absorbed olefinic constituents substantially free from aromatic constituents, passing absorbed oleilnic constituents to an alkylation zone and reacting said constituents with isobutane in the presence of an alkylation catalyst maintained under alkylating conditions whereby branched chain gasoline hydrocarbons of high antiknock value are obtained.

3. The method of manufacturing gasoline of high anti-knock value from unstabilized naphtha containing normally gaseous and normally liquid hydrocarbons including olens and aromatics, which comprises fractionating said unstabilized 05 naphtha to separate a normally gaseous fraction gum-forming constituents, then treating the resultingnaphtha with sulfuric acid of 96-100% strength at a temperature of about 10-60 F. and with short contact time to selectively absorb higher molecular weight olens coextensive in boiling range with aromatic constituents without any substantial absorption of said aromatics, separating said acid with absorbed oletins from the stabilized and treated naphtha. and reacting both olenns of said normally gaseous fraction and absorbed olefin products from said stabilized naphtha fraction. with low-boiling isoparafllns in the presence of an alkylation catalyst under alkylating conditions, whereby an lallerylate of saturated branched chain hydrocarbons boiling within the gasoline range and of high anti-knock value is obtained.

4. The method according to claim 3, wherein at least a portion. of the stabilized and treated naphtha fraction is vsubjected to a reforming operation, and products of reforming are returned to the said unstabilized naphtha fractionation step.

5. 'Ihe method according to claim 3, wherein the stabilized and treated naphtha fraction is distilled to separate a lower boiling fraction from a higher boiling fraction thereof, the higher boiling fraction is subjected to a refonning operation, products of reforming are returned to the unstabilized-naphtha fractionation step, and the lower boiling fraction is blended with the said alkylate.

6. In the manufacture of motor fuel from naphtha containing substantial proportions of olenic and aromatic constituents, the method which comprises subjecting the' naphtha to `intimate and short contactwith concentrated sulfuric acid of .Q6-100% strength at temperatures of about 10-60" F., whereby oleflnic constituents coextensive in boiling range with aromatic confstituents are selectively absorbed without any knock value, extracting the remaining naphtha with a solvent selective for aromatic constituents to thereby recover an aromatic extract from which aromatic constituents can be segregated in concentrated form, reforming at least a portion of said naphtha from which the said olenic and aromatic constituents have been re-4 products to the fraction with acid under conditions to selectively absorb the higher molecular weightoleflns coextensive in boiling range with aromatic constituents without any substantial absorption of said aromatics, separating the acid with absorbed oleflns from the stabilized naphtha, then treating said stabilized naphtha with asolvent selective for aromatics, and separating a solvent extract of aromatic constituents fromthe remaining naphtha, reforming at least a, portion of the remaining naphtha, passing products of said reforming step to the said unstabilized naphtha fractionation step, and reacting both oleilns of said normally'gaseous fraction and absorbed olefin products from said stabilized naphtha fraction with low-boiling isoparaflins in the presence of an alkylation catalyst under alkylating conditions, whereby saturated branched chain hydrocarbons boiling within the gasoline range and of high anti-knock value are obtained.

9. 'I'he method ci' manufacturing gasolineI of high anti-knock value from an unstabilized naphtha containing normally gaseous and normally liquid hydrocarbons including oleiins and aromatics, which comprises fractionating said unstabilized naphtha to separate a normally gaseous fraction containing C4 oleflns from a stabilized normally liquid naphtha fraction containing higher 'molecular weightl oleilns and aromatics, treating said stabilized normally liquid naphtha fraction to remove and separately recover oleflnic compounds and aromatic constituents therefrom which are coextensive in boiling range, reforming at least a portion of the stabilized and treated naphtha from which the said olefins and aromatics have been removed, pass-V oleiins of said normally gaseous 'fractionand olennic compounds from said stabilized normally liquid naphtha fraction with low-boiling iso'- paraifins in the presence of an alkylation catalyst under alkylating conditions, whereby saturated branched chain hydrocarbons boiling within the gasoline range and of high anti-knock value are obtained.

10. In the manufacture of motor fuel from naphtha containing normally ,liquid oleiinic, aromatic and paraihnic hydrocarbon constituents of coextensive boiling range, the methodl which comprises treating said naphtha to remove and separately recover normally liquid olenic and aromatic constituents thereof including the step of extracting said olefinic constituents in the presence of said aromatic constituents with concentrated sulfuric acid of 96-'10% strength at a temperature of about 1060 F. and with short contact time such that normally liquid oleiinic constituents are preferentially absorbed in the acid without any substantial absorption of aromatic constituents, separating the acid containing absorbed normally liquid oleflns,l and alkylating a low-boiling isoparaifln with said absorbed oleins substantially free from aromatics in the presence of an alkylation catalyst under alkylating conditions, whereby branched chain gasoline hydrocarbons of high anti-knock value are obtained.

1l. I'he method of manufacturing a high anti-knock gasoline from naphtha containing olefins, aromatics and paraiiins of coextensive boiling range while at the same time reducing the unsaturation of the naphtha and recovering an aromatic concentrate therefrom, which comprises extracting the cracked naphtha with a solvent selective for aromatic and oleflnic constituents, separating a solvent extract containolens in the acid without any substantial ab-1 sorption of aromatics, separating an aromatic concentrate nom the ma extract, and then alkylating an isoparaiiinwith absorbed olenns substantially free from aromatics in the presence of an alkylation catalyst under alkylating conditions to produce high anti-knock alkylate gasoline.

12. The method according to claim 11, wherein the said extract containing olefinic and aromatic constituents is treated under vmild conditions to remove gum-forming constituents prior to the said acid-olenn absorption step.

13. The method according to claim 11, wherein the alkylate gasoline is blended with at least a portion of the said naphtha ramnate.

14. The method according to claim 11, wherein the naphtha raillnate is separated into lower boiling and higher boiling fractions, the low boiling fraction isvblended with the alkylate, and the higher boiling fraction is reformed and liquid products of the reforming are returned to the solvent treating step.

15. The method which comprises fractionating cracked naphtha to separate a liquid naphtha fraction containing oleiins. treating the said naphtha fraction to remove gum-forming constituents. selectively extracting oleiin constituents from said treated naphtha to provide a charge i'or catalytic alkylation, reforming at least a portion of the treated naphtha from which oleflnic constituents have been extracted, returning products of the reforming operation to the cracked naphtha Afractionating step, and alkylating an isopara with the extracted oletlns in the presence of an aikylation. catalyst under alkylating conditions to produce a saturated alleviate gasoline of' high anti-knock value.'

16. 'I'he method according to claim y15, wherein the treated naphtha from which the oleilnic constituents have been extracted is distilled to separate it into lower boiling and higher boiling fractions, passing the higher boiling fraction to the said reforming operation, and blending the lower boiling fraction with the said alkylate.

ARTHUR R. GOLDSBY. 

